How to use the autovizwidget.autovizwidget.plotlygraphs.bargraph.BarGraph function in autovizwidget

def _get_graph(chart_type):
        if chart_type == Encoding.chart_type_scatter:
            graph = ScatterGraph()
        elif chart_type == Encoding.chart_type_line:
            graph = LineGraph()
        elif chart_type == Encoding.chart_type_area:
            graph = AreaGraph()
        elif chart_type == Encoding.chart_type_bar:
            graph = BarGraph()
        elif chart_type == Encoding.chart_type_pie:
            graph = PieGraph()
        elif chart_type == Encoding.chart_type_table:
            graph = DataGraph()
        else:
            raise ValueError("Cannot display chart of type {}".format(chart_type))

        return graph